DESCRIPTION (applicant's abstract): We will build a peptide "printer" capable of producing, by in situ synthesis, arrays containing at least 1000 unique peptides on a single substrate (glass slide or membrane). The synthesis will be performed by successively microdispensing amino acids using ink-jet technology. Our ten channel printheads, having effective rates of 400 spots per second per channel, will allow 4,000 amino acid spots to be printed in under 1 minute. Using micro-scale synthesis, wash, block, deprotect, and coupling cycles will be reduced from one hour for current macro-scale synthesis, to less than half an hour, thus yielding a synthesis rate of more than one residue per hour. Fifteen-mer peptides will be synthesized in less than 24 hours. The increased density and decreased synthesis time will result in less expensive, higher density arrays than are currently available. Phase I demonstrated that the micro-dispensing can be used to synthesize high purity peptides. In Phase II we will build a prototype printer capable of synthesizing arrays with at least 1000 different peptides. The prototype system will be used to synthesize peptide arrays based on well-characterized proteins. These peptide arrays will be used to validate the synthesis for a large-scale array. Peptide arrays will be produced and evaluated in Proctor & Gamble's drug discovery research. PROPOSED COMMERCIAL APPLICATION: Peptide libraries are used for drug screening/discovery and immunological research (antibodies for diagnostics and protein epitope mapping). Peptide libraries arrays are also an efficient tool for defining protein-protein interaction domains including all receptor-ligand, antibody-antigen interaction. A peptide library-chip with customizable peptide will be used by all of the above.